Re: Integrate vs NIntegrate
- To: mathgroup at smc.vnet.net
- Subject: [mg89150] Re: Integrate vs NIntegrate
- From: dh <dh at metrohm.ch>
- Date: Tue, 27 May 2008 07:14:38 -0400 (EDT)
- References: <g1e35c$er3$1@smc.vnet.net>
Hi Armen,
we cross a branch cut at x=2, as you may see by:
Plot[Re@f[x],{x,0,3}]
If you integrate from 0 to 2 and from 2+epsilon to 3, where epsilon is
small enough for your purpose, you will get the same result from
Integrate and NIntegrate.
hope this helps, Daniel
Armen Kocharyan wrote:
> Dear group,
>
>
> Why do I get different results (Res1, Res2) in Mathematica 6.0.1.0?
>
>
> *q=-1/2; a=0; b=3;*
>
> *h[x_]=(1+x^3)^q;*
>
> *f[x_]=Integrate[h[x],x];*
>
> *Res1=N[f[b]-f[a]]*
>
> *Res2=NIntegrate[h[x],{x,a,b}]*
>
> **
>
> *Res1 = -2.55387-2.42865 i*
>
> *Res2 = 1.65267*
>
>
>
> I'm assuming that Res2 is the correct answer.
>
>
>
> Regards,
>
> Armen
>
>
--
Daniel Huber
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